α频率光刺激脑电信号同步化的初步研究

研究α频率(8～13Hz)闪光刺激是否能引起人脑枕区同频率脑电信号的增加.采集15名正常志愿者在平静、光刺激状态下的脑电信号,利用脑地形图、小波分析和功率谱估计的方法对α频率光刺激前后的脑电信号进行处理,将归一化后的数据分为平静-激活组、男女对照组、两个不同电极位置组进行对比分析,对组间信号的差异进行了讨论,并对受试者精神状态的变化进行初步探讨.结果表明:周期性α频率光刺激能引起大脑枕区同频率脑电的显著增加.通过分析实验数据,初步得到了大脑在外部闪光刺激时脑电的变化规律,本实验结果对研究外部刺激对脑电的影响有一定的参考价值.     

α频率光刺激脑电信号同步化的初步研究

研究α频率（8-13Hz）闪光刺激是否能引起人脑枕区同频率脑电信号的增加。采集15名正常志愿者在平静、光刺激状态下的脑电信号,利用脑地形图、小波分析和功率谱估计的方法对α频率光刺激前后的脑电信号进行处理,将归一化后的数据分为平静-激活组、男女对照组、两个不同电极位置组进行对比分析,对组间信号的差异进行了讨论,并对受试者精神状态的变化进行初步探讨。结果表明：周期性α频率光刺激能引起大脑枕区同频率脑电的显著增加。通过分析实验数据,初步得到了大脑在外部闪光刺激时脑电的变化规律,本实验结果对研究外部刺激对脑电的影响有一定的参考价值。     

基于不同闪烁频率光刺激的脑电压变化研究

目的：脑电信号是大量神经元电活动在大脑头皮表面产生的电位总和,可综合反映大脑内部功能状态和活跃程度。当人体受到外界刺激时,神经系统产生一系列复杂的生物电活动,最终反映为脑电信号。本文使用不同闪烁频率光为刺激源,对光刺激前后脑电信号时域和频域的变化特性进行分析,为利用外刺激调制脑电频率提供新的实验依据。方法：使用同一光源,分别改变其闪烁频率对受试者眼睛进行刺激,利用脑立方移动版采集不同闪烁频率光刺激下的脑电信号,记录并分析脑电信号电位幅值,及其成份δ波（1 Hz~3 Hz）、θ波（4 Hz~7 Hz）、α波（8 Hz~13 Hz）和β波（14Hz~30Hz）能量的变化情况。结果：随着光闪烁频率的增高,脑电压幅度均值和各频段能量先逐渐增大后减小,脑电幅值和各频段能量均在光闪烁频率为5 Hz时达到最大。结论：不同闪烁频率光刺激对脑电压的变化具有显著性影响：在一定阈值之下,脑电压与光闪烁频率变化一致;超过阈值后,趋势相反。该结论有助于探索脑电信号在外刺激作用下的变化规律,为利用外刺激治疗脑部疾病的方式提供了参考价值。     

低频光诱发脑电在浅睡期的样本熵复杂度分析

睡眠障碍患者通常表现为从浅睡期进入深睡期存在困难,分析浅睡期脑电波的变化对研究睡眠效率和睡眠质量至关重要。通过分析低频光刺激下睡眠过程中脑电波的复杂度值变化,研究人在浅睡期脑电波对光刺激的响应,进而探讨外部光刺激对睡眠过程中脑电波的影响。使用美国neuroscan型脑电图仪,采集10例志愿者的光刺激睡眠和正常睡眠的脑电数据。首先,利用时频分析,对睡眠过程中的脑电信号进行分期,获得浅睡期脑电信号;然后,使用小波包分解,获得该期脑电波的各频段分量（δ波、θ波、α波和纺锤波）;接着,采用样本熵算法,分别计算浅睡期脑电信号的复杂度以及各频段脑电波的复杂度;最后,对志愿者在光刺激（5 Hz）和正常睡眠下浅睡期脑电复杂度进行比较,研究光刺激对脑电复杂度的响应情况。结果显示：在低频光刺激下,浅睡期脑电波复杂度的均值为0514 15,明显低于正常睡眠复杂度的均值0589 23,在中央区和顶区有显著性差异（P<005）。研究表明,5 Hz光刺激可诱发浅睡期θ波的同步响应,增强脑电波的节律性,有助于更好地进入深度睡眠。     

20Hz体感振动刺激对脑电特征影响研究

体感振动能够刺激人的体表感觉区,这种刺激传输到躯体感觉神经,进而影响大脑皮层中央后回及中央旁小叶后部的躯体感觉中枢,从而改变大脑功能状态。本研究旨在通过脑电检测方法,研究体感振动对大脑功能状态的影响。分别对12名受试者进行了20Hz体感振动刺激实验,采用相对功率变化率、Lempel-Ziv复杂度和基于互信息的脑网络等方法。结果发现,20Hz振动使得左前额区及左前颞区的脑电信号产生频率跟随响应;而脑网络分析表明:20Hz体感振动刺激使大脑右半脑区的额叶、中央叶、顶叶、颞叶、枕叶之间的信息流传递加强,大脑皮层趋于兴奋。因此,利用20Hz体感振动刺激调节大脑功能状态具有一定可行性。     

基于虚拟现实的不同情绪视频下的脑电谱特性

目的 研究不同情绪类型的虚拟现实(virtual reality,VR)视频刺激下的脑电(electroencephalogram,EEG)特性,通过分析受试者观看VR视频时的EEG能量,探究不同情绪类型VR视频对受试者神经活动的影响.方法 首先制作3种情绪类型(正性、中性、负性)的VR视频,招募30名健康受试者(男15人,女15人),让他们观看这些视频,并完成情绪评价,同时采集他们观看任务时的8通道EEG信号.然后对EEG信号做预处理,包括滤波、去除坏导联及坏段、去除眼电成分、插值及重参考.对处理干净的信号通过小波变换进行分频,检测θ、α、β频带的信号能量.结果 正性和中性刺激下在全脑范围的各频带脑电能量都显著高于负性刺激;无论何种情绪的VR视频刺激,都表现出右半球的θ能量显著大于左半球的偏侧化现象,且额区和顶区的α能量都显著高于颞区.结论 VR情绪视频能有效诱发特定的情绪,且在VR情绪视频刺激下,存在显著的负性偏向,即负性VR刺激下表现出与正性和中性VR刺激不同的脑电谱特性,表明VR下负性情绪对大脑活动影响的特异性.     

智力低下儿童脑电地形图研究

对34例智力低下儿童进行了清醒闭目,睁眼及深呼吸后三种状态下脑电地形图的统计分析,与正常同年令组儿童对比,发现下述有价值特点:1.慢波功率值增高,且颞区增高较其它功能区更明显。2.枕部α波前移。3.α最大功率与最小功率自然对数比明显下降。4.各状态下脑电活性差异减小。以上改变,提供了脑电综合参数有可能成为智力检测客观指标之一。     

下肢临近关节稳态体感诱发电位的提取和分析

稳态体感诱发电位（SSSEP）在提升运动想象脑机接口分类性能方面有着显著作用，因此如何有效提取SSSEP是研究的重点。为有效提取下肢膝-踝临近关节处的SSSEP，设计体感刺激参数筛选试验，分别采集10名受试者在右腿腘窝和右脚踝内侧处10种不同电刺激频率下的脑电信号，使用快速傅里叶变换、时频图谱和脑地形图进行综合分析。结果显示，受试者在右脚踝内侧的频谱特征优于右腿腘窝，33 Hz为最优刺激频率，能用于下肢的电刺激强度为10~20 mA。     

脑电信号与经穴输入信号相关分析的实验研究

利用不同频率电脉冲信号作用于人体不同经穴上，通过对经穴输入信号与脑电波输出信号之间的相关性研究，探索一种经穴优化输入的新方法，确立经络与大脑之间的动态关联性。实验研究表明30Hz的断续波电脉冲刺激信号与其诱发的脑电α2波相关性最强，使用30Hz的断续波电脉冲刺激天枢、大肠俞这组穴位有利于诱发大脑的有益波态α波。     

睡眠剥夺下警觉度变化的非线性研究

本文采用Lempel-Zin复杂度与脑电地形图(BEAM)相结合的方法研究睡眠剥夺(SD)下警觉度的变化过程。10名受试者进行了36h的SD,并且每6h进行了自发和Oddball听觉诱发实验,记录了自发脑电(EEG)和诱发EEG,构建了基于复杂度的脑电地形趋势图。结果表明,36hSD中,警觉度可以分为三个阶段:前12h为警觉度较高的阶段,中间12h为警觉度快速下降的阶段,最后12h为警觉度较低的阶段。在SD过程中,自发EEG的复杂度在全脑范围内有不同程度的下降,与主观量表的趋势相符;诱发EEG的额叶复杂度降低,其趋势与行为学结果相符。所以,EEG复杂度可以有效地反映大脑警觉度的变化,且复杂度计算简单、运算速度快,为以后应用于警觉度的实时监测提供了新的途径。     

Visually evoked phase synchronization changes of alpha rhythm in migraine: correlations with clinical features.

OBJECTIVE: This study aimed to compute phase synchronization of the alpha band from a multichannel electroencephalogram (EEG) recorded under repetitive flash stimulation from migraine patients without aura. This allowed examination of ongoing EEG activity during visual stimulation in the pain-free phase of migraine. METHODS: Flash stimuli at frequencies of 3, 6, 9, 12, 15, 18, 21, 24, and 27 Hz were delivered to 15 migraine patients without aura and 15 controls, with the EEG recorded from 18 scalp electrodes, referred to the linked earlobes. The EEG signals were filtered in the alpha (7.5-13 Hz) band. For all stimulus frequencies that we evaluated, the phase synchronization index was based on the Hilbert transformation. RESULTS: Phase synchronization separated the patients and controls for the 9, 24 and 27 Hz stimulus frequencies; hyper phase synchronization was observed in patients, whereas healthy subjects were characterized by a reduced phase synchronization. These differences were found in all regions of the scalp. CONCLUSIONS: During migraine, the brain synchronizes to the idling rhythm of the visual areas under certain photic stimulations; in normal subjects however, brain regions involved in the processing of sensory information demonstrate desynchronized activity. Hypersynchronization of the alpha rhythm may suggest a state of cortical hypoexcitability during the interictal phase of migraine. SIGNIFICANCE: The employment of non-linear EEG analysis may identify subtle functional changes in the migraine brain.     

k-Nearest neighbour local linear prediction of scalp EEG activity during intermittent photic stimulation

The characterization of the EEG response to photic stimulation (PS) is an important issue with significant clinical relevance. This study aims to quantify and map the complexity of the EEG during PS, where complexity is measured as the degree of unpredictability resulting from local linear prediction. EEG activity was recorded with eyes closed (EC) and eyes open (EO) during resting and PS at 5, 10, and 15 Hz in a group of 30 healthy subjects and in a case-report of a patient suffering from cerebral ischemia. The mean squared prediction error (MSPE) resulting from k-nearest neighbour local linear prediction was calculated in each condition as an index of EEG unpredictability. The linear or nonlinear nature of the system underlying EEG activity was evaluated quantifying MSPE as a function of the neighbourhood size during local linear prediction, and by surrogate data analysis as well. Unpredictability maps were obtained for each subject interpolating MSPE values over a schematic head representation. Results on healthy subjects evidenced: (i) the prevalence of linear mechanisms in the generation of EEG dynamics, (ii) the lower predictability of EO EEG, (iii) the desynchronization of oscillatory mechanisms during PS leading to increased EEG complexity, (iv) the entrainment of alpha rhythm during EC obtained by 10 Hz PS, and (v) differences of EEG predictability among different scalp regions. Ischemic patient showed different MSPE values in healthy and damaged regions. The EEG predictability decreased moving from the early acute stage to a stage of partial recovery. These results suggest that nonlinear prediction can be a useful tool to characterize EEG dynamics during PS protocols, and may consequently constitute a complement of quantitative EEG analysis in clinical applications.     

Movement rate effect on activation and functional coupling of motor cortical areas

We investigated changes in the activation and functional coupling of bilateral primary sensorimotor (SM1) and supplementary motor (SMA) areas with different movement rates in eight normal volunteers. An auditory-cued repetitive right-thumb movement was performed at rates of 0.5, 0.75, 1, 2, 3, and 4 Hz. As a control condition, subjects listened to pacing tones with no movements. Electroencephalogram (EEG) was recorded from 28 scalp electrodes and electromyogram was obtained from the hand muscles. The event-related changes in EEG band-power (ERpow: activation of each area) and correlation (ERcor: functional coupling between each pair of cortical areas) were computed every 32 ms. Modulations of ERpow and ERcor were inspected in alpha (8-12 Hz) and beta (16-20 Hz) bands. Motor cortical activation and coupling was greater for faster movements. With increasing movement rate, the timing relationship between movement and tone switched from synchronization (for 0.5-1 Hz) to syncopation (for 3-4 Hz). The results suggested that for slow repetitive movements (0.5-1 Hz), each individual movement is separately controlled, and EEG activation and coupling of the motor cortical areas were immediately followed by transient deactivation and decoupling, having clear temporal modulation locked to each movement. In contrast, for fast repetitive movements (3-4 Hz), it appears that the rhythm is controlled and the motor cortices showed sustained EEG activation and continuous coupling.     

基于节律同化效应的思维脑电信号分类研究

通过对正弦调制光（SML）刺激和无刺激思维脑电信号的对比分类研究，探索了思维脑电信号的节律同化现象对思维脑电信号分类的影响。研究结果表明，大脑在SML刺激下进行思维作业时，思维EEG信号携带的与刺激频率有关的节律同化信息能提高某些思维作业的分类正确率，并且SML刺激产生的局部节律同化效应能减少用于提供分类信息的EEG信号的导联数。这些结果有利于提高基于思维作业脑-计算机接口（BCI）的通信准确率和速度。     

Alpha-generation as basic response-signature to transcranial magnetic stimulation (TMS) targeting the human resting motor cortex: a TMS/EEG co-registration study

The effects of repetitive transcranial magnetic stimulation (rTMS) on cortical excitability are usually inferred from indirect indexes, such as EMG responses. It has now become possible to directly evaluate rTMS impact by means of concurrent EEG recording. The aim of this study was to examine the modulation induced by high frequency rTMS (20 Hz) over left primary motor cortex on the ongoing oscillatory activity. Thirteen subjects underwent two sham and a real rTMS session while acquiring EEG. Event-related desynchronization/synchronization was calculated for the α and β bands. rTMS induced a dose-dependent increase in synchronization in both bands over central and parietal sites. The strongest effect found for the α band outlasted the end of the stimulation. Considering previous studies, our data suggest that α generation may represent an intrinsic induced response and a basic response signature to TMS targeting the human resting motor cortex.     

Evaluating the relationship of non-phase locked activities in the electroencephalogram during intermittent stimulation: a partial coherence-based approach

Partial coherence estimate between two signals removing the contribution of a periodic, deterministic one is proposed for measuring the coherence between two ongoing eletroencephalografic (EEG) activities collected at distinct cortical regions under sensory stimulation. The estimator expression was derived and shown to be independent of the stimulating signal. Simulations were used for obtaining the critical values for this coherence estimate. The technique was also evaluated throughout simulations and next applied to the EEG from 12 subjects under intermittent photic stimulation at 4 and 6 Hz. In both simulation and EEG data, major differences between partial and simple coherences occurred at the stimulation frequency and harmonics, except for those falling within the alpha band. These findings suggest that the technique is highly selective in removing the contribution of the periodic source. They also indicate high coherence values of the ongoing EEG within the alpha band.     

Different EEG topographic effects of painful and non-painful intramuscular stimulation in man

To clarify the specific effects of muscle pain on electroencephalogram (EEG) activation in man, painful and non-painful sensations were produced by intramuscular injections of capsaicin and vehicle solution in the left brachioradialis muscle, with identical procedures in 15 male volunteers. Thirty-one channel EEG data acquired before, during and after the two injections were analysed and compared in respect of topography and power spectrum. Although the painful and non-painful muscular stimulations evoked similar EEG topographic patterns, statistics demonstrated that distinct EEG activation over different areas of the head were induced by the painful and non-painful stimulation compared with the baselines. The decreases in theta and alpha-1 (8-10.5 Hz) activity in central and posterior parietal parts were evoked by non-painful stimulation, but the decreases in alpha-1 and alpha-2 (11-13.5 Hz) activities in the posterior part of the head were induced by painful stimulation. The alpha-2 activity augmented during the waning pain following a decrease in the overt pain. Comparing the EEG changes between baseline, non-painful and painful stimulations as well as waning pain, we found that the increase in beta-2 activity during muscle pain was significant over the extensive areas of the head, whereas a significant increase in alpha-2 activity took place at the posterior part of the head during waning pain following a marked decrease in overt pain. These results may imply that the painful and non-painful muscular stimulations evoke distinct EEG activation in different neural networks of the human brain and the intensity of nociceptive input from muscle may encode the variety of topographic EEG changes.     

Periodic behavioral changes during hippocampal theta rhythm elicited by septal stimulation in rats

The influence of an electrical stimulation of the medial septum on the electroencephologram of the dorsal hippocampus and behavior was studied in freely moving rats. A short stimulation at 4–12 Hz frequency always induced orienting behavior (searching, rearing, sniffing, exploration) as soon as hippocampal rhythmic slow activity, or theta rhythm is elicited. An increase in stimulation intensity or in pulse duration led to an increased occurrence of theta rhythm and likewise, to an increase of orienting behavior. Both the theta rhythm and orienting behavior were dependent on the stimulation frequency.During long-lasting septal stimulation at 7 Hz, which elicited a continuous hippocampal theta rhythm, periodic behavioral changes were observed, consisting of orienting behavior alternating with grooming behavior (cleaning, washing, licking, scratching). These rhythmic periods lasted for 3–5 min.The significance of the rhythmic behavioral changes are discussed in relation to the activity of the cholinergic septohippocampal system and to rapid-eye-movement sleep and memory consolidation.     

Effect of body position on bilateral EEG alterations and their relationship with autonomic nervous modulation in normal subjects

This study investigated the effect of body position on the electroencephalogram (EEG) and autonomic nervous modulation, and the relationship between them using spectral analysis of EEG and heart rate variability (HRV). All healthy volunteers recruited had their electrocardiogram and EEG recorded for power spectral analysis. We found that when changing position from supine to upright, the EEG spectral components below the α band, such as δ and θ bands, were significantly decreased while the EEG spectral components above the α band, such as β, γ and ω bands, were significantly increased in both scalps. Correlation analysis showed that the θ rhythm of both scalps might be associated with the control of HR, the α and β rhythms of right scalp might be associated with vagal modulation, and the γ rhythm of left scalp might be associated with sympathetic modulation of the subject. Thus, some EEG components might be associated with the autonomic nervous modulation of the subject during positional change. There might be a mechanism located in the brain-stem which jointly controls both autonomic influences on heart rate and EEG activation.